Onset/offset characteristics and intubating conditions of rapacuronium: A comparison with rocuronium

We compared onset and offset of action and tracheal intubating conditions after rapacuronium and rocuronium in 60 patients in a randomized, assessor-blinded study. Following induction of anaesthesia with propofol 2.5 mg kg^-1, either rapacuronium 1.5 mg kg^-1 (n=30) or rocuronium 0.6 mg kg^-1 (n=30) was administered to facilitate tracheal intubation. Anaesthesia was maintained with either a propofol infusion (100 μg kg^{- 1} min^-1) or sevoflurane (1% end-tidal) with 66% nitrous oxide (N₂O), n=15 in each subgroup. Neuromuscular monitoring was performed using an electromyographic (EMG) device (Datex Relaxograph). The lag times (mean 42 (SD II) s and 44 (16) s), maximum block (99 (2)% and 98 (3)%) and intubating conditions at 60 s (good-to-excellent in 86% and 84% of patients) were similar for rapacuronium and rocuronium, respectively. The onset time of rapacuronium was shorter than rocuronium (87 (20) vs 141(65) s, P<0.001), and the degree of block at 60 s was greater (69 (26) vs 50 (27)%, P<0.05). Twenty-five per cent recovery was shorter with rapacuronium than rocuronium during propofol (15.0 (3.2) vs 39.1 (14.2) min, P<0.001) and sevoflurane (15.1 (4.2) vs 47.8 (19.0) min, P<0.001) anaesthesia. We conclude that rapacuronium 1.5 mg kg^-1 had a more rapid onset, similar intubating conditions, and shorter recovery times than rocuronium 0.6 mg kg^-1.